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NAME
MPI_Wtime - Returns an elapsed time on the calling processor.
SYNTAX
C Syntax
#include <mpi.h>
double MPI_Wtime()
Fortran Syntax
INCLUDE 'mpif.h'
DOUBLE PRECISION MPI_WTIME()
C++ Syntax
#include <mpi.h>
double Wtime()
RETURN VALUE
Time in seconds since an arbitrary time in the past.
DESCRIPTION
MPI_Wtime returns a floating-point number of seconds, representing
elapsed wall-clock time since some time in the past.
The "time in the past" is guaranteed not to change during the life of
the process. The user is responsible for converting large numbers of
seconds to other units if they are preferred.
This function is portable (it returns seconds, not "ticks"), it allows
high resolution, and carries no unnecessary baggage. One would use it
like this:
{
double starttime, endtime;
starttime = MPI_Wtime();
.... stuff to be timed ...
endtime = MPI_Wtime();
printf("That took %f seconds\n",endtime-starttime);
}
The times returned are local to the node that called them. There is no
requirement that different nodes return the "same" time.
NOTES
The boolean variable MPI_WTIME_IS_GLOBAL, a predefined attribute key
that indicates whether clocks are synchronized, does not have a valid
value in Open MPI, as the clocks are not guaranteed to be synchronized.
This is intended to be a high-resolution, elapsed (or wall) clock. See
MPI_Wtick to determine the resolution of MPI_Wtime.
This function does not return an error value. Consequently, the result
of calling it before MPI_Init or after MPI_Finalize is undefined.
Open MPI 1.2 September 2006 MPI_Wtime(3OpenMPI)
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